The present invention relates to display apparatuses such as plasma displays, electroluminescence displays, and light emitting diode displays.
Conventionally, a light-emitting type display apparatus such as a plasma display, an electroluminescence display or a light emitting diode display generally emits light to display when it has some amount of information that should be displayed. The display apparatus inevitably involves large power consumption as the amount of information to be displayed becomes large. Therefore, it has been studied to restrict power consumption when the amount of display data has become large. In Japanese Patent Laid-Open Publication No. H08-65607, it is disclosed that depending on average luminance signal level of images, an automatic power control (APC) section adjusts the light emission amount per unit area (luminance) of a display in response to variations in the average luminance signal level so that the power consumption is controlled so as not to increase excessively.
FIG. 11 is a block diagram showing the configuration of the display apparatus according to the prior art disclosed in the publication. R, G and B signals as picture signals are fed into their corresponding terminals. The R, G and B signals via their corresponding terminals are fed into a Y-encode circuit 61 which encodes the R, G and B signals into a luminance signal (hereinafter, referred to as Y signal) to output. A digital luminance integrating circuit 62 inputs and integrates the Y signal from the Y-encode circuit 61 to output an average luminance.
Taking as a parameter the average luminance outputted from the digital luminance integrating circuit 62, a memory controller 63 receives data corresponding to the average luminance from a memory 64 to output the data to an automatic power controller 66 of a plasma display apparatus 68. The automatic power controller 66 outputs to a PDP (plasma display panel) display section 67 a control signal for adjusting the light emission amount per unit area (luminance) of the PDP display section 67 in response to the data from the memory control section 63, thereby power consumption is controlled.
However, the power consumption at the PDP display section 67 is not proportional to the luminance signal. For example, with a common transform equation, Y=0.3R+0.59G+0.11B, used in the Y-encode circuit 61, the ratio among their respective luminance signals (YR, a luminance signal for display of single red; YG, a luminance signal for display of single green; and YB, a luminance signal for display of single blue) is YR: YG: YB =0.3:0.59:0.11 when single color of red (hereinafter, expressed as R), green (hereinafter, expressed as G) and blue (hereinafter, expressed as B) are displayed,. Here, the luminance signal YG for the display of G is the largest and the luminance signal YB for the display of B is the smallest so that different control processes are performed by the automatic power controller 66 for the respective cases of the display of the single color depending on the average luminance. Ratio among respective coefficients (0.3, 0.59,0.11) for obtaining luminance signals in the transform equation equals to a ratio at which human eyes feel the brightness with each three primary colors (R, G, B), and do not show any power consumption ratio. Therefore, it may cause inappropriate control to be performed.
As shown above, in the technique of the prior art, with average luminance used as a parameter for the power consumption control of a display apparatus, light emission amount (luminance) of the display section 67 would be recognized as less than required amount in the case of an image in which green components occupy a larger portion than the other colors, and power consumption would be recognized as more than the performance of the power supply 65 in the case of an image in which blue components occupy a larger portion than the other colors. Thus, it has been a problem of the prior art technique that an accurate automatic control of power consumption or light emission amount cannot be achieved.
In order to solve the above problem, a display apparatus of the present invention is characterized in that the light emission amount (luminance) or power consumption is controlled based on a power prediction signal obtained by weighted average levels of individual colors with coefficients representing ratios of power consumptions involved in data display when the three primary colors of red, green and blue are displayed in single colors, respectively, or representing ratios of phosphor areas of the individual colors, and by then summing up the weighted average levels.
According to the present invention, since the power consumption or light emission amount (luminance) is controlled based on a power prediction signal computed with coefficients representing power consumption ratios or phosphor area ratios, it becomes possible to control the power consumption or light emission amount (luminance) independently of the hue of input picture signals.
In a first aspect of the invention, a display apparatus comprises an emission unit, integrating circuits, three multiplying circuits, a power consumption prediction circuit, a controller and a brightness control circuit.
The emission unit emits light to display images. The integrating circuits integrate input picture signals of R (red), G (green) and B (blue) for each predetermined period to output an average level of R signal, an average level of G signal and an average level of B signal, respectively. The first, second and third multiplying circuits multiplies the R average level, the G average level and the B average level by their respective parameters KR, KG and KB, respectively. The power prediction circuit adds output signals from those multiplying circuits together to obtain and output a power prediction signal. The signal indicates amount of power predicted or expected to be consumed on the emission unit. The controller receives the power prediction signal to output a control signal based on a value of the received signal. The brightness control circuit controls light emission amount per unit area according to the control signal.
In the display apparatus, a ratio of parameters KR, KG and KB may be determined to be equal to a ratio of powers consumed for display each color of red, green and blue with same brightness. In this case, the display apparatus can control the power consumption or light emission amount (luminance) more accurately, as compared with the prior art technique in which power consumption of the display apparatus is controlled with average luminance.
In a second aspect of the invention, a display apparatus comprises an emission unit, integrating circuits, first, second and third multiplying circuits, a power consumption prediction circuit, a controller, a delay circuit and a first, second and third multiplying circuits.
The emission unit emits light to display images. The integrating circuits integrates input picture signals of R, G and B for each predetermined period to output an average level of R signal, an average level of G signal and an average level of B signal, respectively. The first, second and third multiplying circuits multiplies the R average level, the G average level and the B average level by their respective parameters KR, KG and KB, respectively. The ratio of parameters KR, KG and KB is determined to be equal to a ratio of powers consumed for display each color of red, green and blue with same brightness. The power consumption prediction circuit adds output signals from the multiplying circuits together to obtain and output a power prediction signal. The signal indicates amount of power expected to be consumed on the emission unit. The controller receives the power prediction signal to output a multiplying coefficient based on a value of the received signal. The delay circuit delays the input picture signals of R, G and B to output the delayed picture signals DR, DG and DB, respectively. The fourth, fifth and sixth multiplying circuits multiplies the delayed picture signals DR, DG and DB by the multiplying coefficient, respectively.
In a third aspect of the invention, a display apparatus for dividing one field of picture signal into a plurality of subfields weighted respectively, and then displaying images of subfields in superimposition on time region to realize gradation expression.
The display apparatus comprises an emission unit, R, G and B integrating circuits, multiplying circuits, a power consumption prediction circuit, a controller, a delay circuit, picture signal-subfield associating circuit, a subfield pulse generator.
The emission unit emits light to display images. The R integrating circuit, G integrating circuit and B integrating circuit integrates at least one field of input picture signals of R, G and B to output an average level of R signal, an average level of G signal and an average level of B signal, respectively. The multiplying circuits multiplies the R average level signal, the G average level signal and the B average level signal by parameters KR, KG and KB determined based on the ratio of powers consumed for display each color of red, green and blue. The power consumption prediction circuit adds output signals from the first, second and third multiplying circuits together to obtain and output a power prediction signal. The signal indicates power expected to be consumed on the emission unit. The controller receives the power prediction signal to output a emission pulse control signal for selecting one of light emission types in response to a value of the received signal. The delay circuit for delaying the input picture signals R, G and B to output the delayed picture signals DR, DG and DB, respectively. The picture signal-subfield associating circuit receives the emission pulse control signal and the delayed picture signals DR, DG and DB, and associates output signals from the delay circuit with subfield structure of the light emission type based on the emission pulse control signal. The subfield pulse generator receives the emission pulse control signal, and generates pulses in the subfield structure corresponding to the light emission type based on the emission pulse control signal. The pulses include at least one of scanning pulses, sustaining pulses and erasing pulses.
In a forth aspect of the invention, a display apparatus for displaying images of subfields in superimposition on time region to display data with gradation, by dividing one field of picture signal into a plurality of subfields weighted.
The display apparatus comprises an emission unit, R, G and B integrating circuits, first, second and third multiplying circuits, a power consumption prediction circuit, a controller, a delay circuit, forth, fifth and sixth multiplying circuits, a picture signal-subfield associating circuit, a subfield pulse generator.
The emission unit emits light to display images. The R integrating circuit, G integrating circuit and B integrating circuit integrates at least one field of input picture signals of R, G and B to output an R average level signal, a G average level signal and a B average level signal, respectively. The multiplying circuits multiplies the R average level signal, the G average level signal and the B average level signal by respective parameters KR, KG and KB obtained by a ratio of powers consumed for display each color of red, green or blue. The power consumption prediction circuit adds output signals from the multiplying circuits together to obtain and output a power prediction signal. The signal indicates power expected to be consumed on the emission unit. The controller receives the power prediction signal to output a emission pulse control signal and a multiplying coefficient according to a value of the received signal. The emission pulse control signal is available for selecting one of light emission types, the multiplying coefficient is available for equalizing gray scale level at a border of adjacent emission types. The multiplying coefficient is obtained based on the power prediction signal from the controller. The delay circuit delays the input picture signals of R, G and B to output delayed picture signals DR, DG and DB, respectively. The fourth, fifth and sixth multiplying circuits multiplies the delayed picture signals DR, DG and DB by a multiplying coefficient for collecting gray scale level so as to equalize gray scale level between adjacent emission types at changeover point of those emission types, respectively. The picture signal-subfield associating circuit receives the emission pulse control signal and the signals of the fourth, fifth and sixth multiplying circuits as inputs, and associates the received signals from the fourth, fifth and sixth multiplying circuits with subfield structure of a light emission type responsive to the emission pulse control signal. The subfield pulse generator receives the emission pulse control signal, and generates pulses including scanning, sustaining, erasing pulses with the subfield structure of a light emission type responsive to the emission pulse control signal.
In the display apparatus described above, a ratio of the parameters KR, KG and KB may be equal to a ratio of area of phosphors for each color of red, green and blue. Since the areas of the phosphors are generally proportional to the power consumption, the power prediction signal can be estimated in a simplified manner by weighting the individual color average levels with coefficients representing the area ratios of the phosphors and then summing up the weighted average levels.